[Haskell-cafe] Read lines of a file into a Vector

[Tobias Dammers]

If I'm not mistaken, lazy lists and lazy IO alone make this a reasonably
efficient implementation; even without further optimizations, the
intermediate lists would most likely never reside in memory all at once.

On Aug 11, 2016 9:27 AM, "Oleg Grenrus" <oleg.grenrus at iki.fi> wrote:

> Thanks to the lazy IO, deforestration and fusion framework in `Vector`,
>
>     readLines h = fromList . lines <$> hGetContents h
>
> shouldn’t create intermediate lists or/and read the whole file at once
> into memory.
>
> - Oleg
>
>
> On 11 Aug 2016, at 10:03, Jake <jake.waksbaum at gmail.com> wrote:
>
> I want to write a function that will read the contents of a file and
> return a Vector of its lines:
>
> readLines :: Handle -> IO (Vector String)
>
> I have an implementation that works but seems to naive and inefficient to
> me because it reads the entire file contents, *then *splits it into
> lines, and *then* converts it to a Vector from a list.
>
> readLines h = fromList . lines <$> hGetContents h
>
> I would like to a) use hGetLine and continue until I get an isEOFError and
> b) read directly into a Vector instead of a list. I started something using
> Data.Vector.unfoldr but I the presence of the IO monad around my String was
> causing issues I couldn't figure out how to solve.
>
> I'd also be curious to see how to do either one of these things separately
> and I assume they'd each help make my program more efficient on their own.
> Or, maybe my implementation is not as terrible as I thought because some
> laziness/fusion/optimization magic is happening behind the scenes?
>
> Thanks,
> Jake Waksbaum
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
>
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/haskell-cafe/attachments/20160811/1fb08287/attachment.html>